There are many different types of tumors and cancers. Gliomas are the most common type of primary brain tumors and are thought to arise from glial cells, or precursors of glial cells, that surround, support, and cooperatively interact with neurons in the brain. Because gliomas generally have already extensively invaded brain tissue before a patient is aware of the disease, gliomas are generally not curable. Glioblastomas are the most malignant and most commonly occurring type of gliomas in adults, representing about 50 percent of all gliomas. Glioblastomas are distinguished by necrosis, or tissue death, within the central portion of the tumor or irregularly spaced between vascular tissues, and by a surrounding shell of tissue diffusely invaded by peripheral tumor cells and characterized by edema. The aggressive behavior of glioblastomas is reflected in the nearly 100 percent fatality rate of patients suffering from this type of tumor within approximately two years following diagnosis, even after extensive medical intervention, including surgery, radiotherapy, and chemotherapy.
Despite continual advancements in imaging technologies, glioma cells generally invade far beyond the regions recognized as being abnormal using various types of clinical imaging technologies, including computer-aided tomography (“CT”), magnetic-resonance imaging (“MRI”), and positron emission tomography (“PET”). The extent of glioma-cell invasion is generally greater than that assumed for current radiotherapy-treatment planning. Currently, an additional shell of tissue invaded by glioma cells, having a thickness of approximately two centimeters, is assumed to surround the volume of the tumor seen in CT, MRI, or PET images. Because the extent of glioma-cell invasion is currently inaccurately modeled, therapies based on understanding the extent of glioma-cell invasion are often misapplied, leaving certain of the glioma cells that have diffused away from the tumor mass untreated or inadequately treated. The medical community continues to seek improved methodologies for characterizing both the extent of glioblastomas and other tumors as well as determining the aggressiveness of tumors and additionally characterizing the tumors in order to guide medical interventions as well as provide accurate prognoses for patients.